Quantum theory, also known as quantum mechanics or quantum physics, is a set of particle laws mainly applied to atoms or smaller entities on a very small scale. The core of quantum theory is the combination of uncertainty principle and wave-particle duality concept.
Every entity in the quantum world has the characteristics of Po River particles, and we are used to treating Po River particles as completely different things. For example, light, which is usually regarded as electromagnetic waves, behaves like a particle flow (called photons) in some cases. Max at the end of 19 Planck found that only when atoms emit and absorb light in the form of discrete quanta (photons) can the nature of blackbody radiation be explained. This discovery makes physicists understand the difference between quantum physics and classical mechanics. The fundamental point of Planck's discovery is that there is a limit to how small the change of atomic energy can be; In modern terms, the limit of this change is relative to the emission or absorption of a single photon. The significance of "quantum jump" is that this jump is the smallest possible change; Therefore, when advertisements and politicians say that they have made great progress, they inadvertently reveal their honesty.
Planck himself did not mention photons, but he interpreted blackbody radiation as the result that atoms could not emit energy except in discontinuous shares. Nor does he think that light itself can be considered to be composed of particles. Is that Albert? Einstein first proved that light can be regarded as a particle in a paper published in 1905 (for which he won the Nobel Prize). This idea developed into the boson theory of light in the1920s. Also in 1920s, the experiment proves that the typical elementary particle-electron also has the characteristics of wave. However, the essence of wave-particle duality is clearly shown in modern experiments that show the dual nature of waves and particles of electrons.
These experiments are based on "double-slit" experiments, which are often used to prove that light propagates like waves (for example, in science classes in middle schools). In this experiment, the light passes through a small hole on the screen and shines on the second screen with two small holes. The light from either of the two holes on the second screen continues to the third screen, where it forms a pattern of bright spots and dark spots. The traditional explanation for this speckle pattern is that waves from two holes reach all parts of the last screen. When the two beams of light have the same speed, they will be superimposed into a Liang Cheng spot; When two beams of light are out of sync, they will cancel each other, leaving a dark spot. Exactly the same phenomenon occurs in the ripples caused by throwing two small stones into the pond at the same time-in some places, the ripples increase, while in others, the ripples disappear. So this double-hole experiment proves that light travels like waves.
In the modern experiments conducted by Japanese scientists at the end of1980s, the light source was replaced by an electronic "gun" that could emit one electron at a time. The role of these two holes is played by the magnetic field, and the final screen is a detector similar to a TV screen. Each electron passing through the experimental device must reach the screen of the detector through one of two paths (one of two "holes"). Sure enough, when an electron is injected into the experimental device, each electron will trigger an accurate light spot, corresponding to the arrival event of a single particle on the screen. However, when a large number of electrons are injected into the experimental device one by one, a large number of light spots on the screen form a pattern of alternating light and dark, which is exactly the same as the interference pattern displayed by the waves that arrive at the screen through two small holes at the same time.
The great physicist Richard? Fei Enman (19 18-88) once said that the double-hole experiment contains the "core secret" of quantum mechanics, and no one knows what happened inside. It not only means that quantum entities move like waves, but also arrive and leave like particles. They seem to know the past and the future. It seems that electrons start from the electron gun in the form of particles, then propagate in the form of waves and enter the experimental device through two routes, and then become particles again to reach an exact position on the screen. Moreover, each electron will choose a correct place to trigger a light spot, thus making its own contribution to the interference pattern that took a long time to form. How on earth does it "know" all other electrons and where other electrons will fall in the pattern? A very weak light source is also used in the classical double-hole experiment, so that only one photon enters the experimental device at a time. Similarly, they also form interference patterns on the final screen.
The standard interpretation of all this is called Copenhagen interpretation (because it was mainly put forward by scholars in Copenhagen). This explanation holds that when the equivalent fruiting body moves, it propagates like a wave that strictly obeys the law of probability, so that it can be calculated where the wave is the strongest (that is, where the chances of finding electrons or any other particles are the greatest) and where the wave is the weakest. When observing or measuring (for example, when an electron wave hits the detector screen), the "wave function" collapses into a point particle. At that moment, the probability of finding electrons anywhere else becomes zero, but as long as the quantum entity is no longer observed, the probability immediately spreads from the last observed place.
Although there are many disappointments, the Copenhagen interpretation can be used to predict the experimental results involving fruiting bodies such as electrons and protons, and it is also the physical basis for developing lasers, computer chips and many other utensils, as well as understanding complex biomolecules such as deoxyribonucleic acid. But the prominence of Copenhagen's interpretation, like other things, is largely a historical accident. Although Copenhagen explanation is regarded as the standard version of quantum theory by physicists because it is the first available explanation, it is only one of several explanations, all of which are unsatisfactory, but they can all give the same "answer" in similar calculations. For many people, this means that none of these explanations can correctly understand what is happening in the quantum horizon; Therefore, before the quantum theory is firmly established, it is necessary to have a new understanding of related physical phenomena.
To gain a new understanding, it may be necessary to complete a rational leap. Some explanations of quantum mechanics require that signals propagate backward in time, while all explanations require that particles can exchange information with each other instantly even if they are far apart. These may be signs of a rational leap.
However, quantum theory can be used to calculate the properties of atoms and other particle systems, just like a cookbook. You can bake cakes according to the recipe without knowing the physical process in the oven. Similarly, you can use quantum laws to calculate the spectrum of hydrogen without knowing what is happening in the quantum world. Therefore, the study of the universe by spectroscopy directly depends on the knowledge about atoms and molecules provided by quantum theory. The nature of nucleus also depends on quantum process, so our understanding of nuclear synthesis and the internal productivity reaction of stars also depends on quantum theory. For example, it is quantum uncertainty that explains how alpha particles escape from the nucleus (through tunneling effect) when alpha decays, and also explains why the nuclei can overcome the repulsion of their own positive charges and get together under the internal conditions of stars. Because the position of nuclei is uncertain, they extend more than the corresponding classical particles, so even though classical mechanics says they are too far apart to converge, they can "overlap" and converge with each other. The success of the model describing how all this happened inside the sun in predicting many observed properties of the sun (including its central temperature) is one of the best large-scale symbols, indicating that quantum physics is indeed an appropriate description of things at this level (at least in the sense of cookbooks).
The most important intersection between quantum physics and cosmology is Weiner in1920s. Heisenberg's uncertainty principle. It is related to wave-particle duality, which can be explained most clearly by the uncertainty of the position and momentum of the object, that is, the understanding of the object's whereabouts. Position is obviously the property of particles, and you can tell exactly where a classic particle is. It is also obvious that you can't tell where the classical wave is, but only point out the spatial area where the wave passes, because the nature of the wave determines that it is an outward expansion thing. In the world of classical mechanics, waves and particles do not have the same position, but they do have a direction-they have momentum and know where they are going.
Heisenberg proved that there are inherent uncertainties in the understanding of position and momentum in the quantum world. You can never know the position and momentum of an entity like an electron at the same time, which will strengthen the "volatility" of the entity and make it expand and its position uncertain. If you try to measure its position accurately, it will make its fluctuation uncertain, so it is impossible to determine where it is going. The magnitude of the position uncertainty multiplied by the magnitude of the momentum uncertainty must always be equal to or greater than a certain value, which is equal to Planck's constant divided by 2π (this value is recorded as h and pronounced as "h bar").
This is not the result of the difficulty of measurement test. Of course, it is undoubtedly difficult to measure the position and momentum of a single electron. Just when you measure (probably by bouncing photons back by electrons), you are also changing the properties you are trying to measure, because electrons bounce back because of the impact of photons. But quantum uncertainty is the real attribute of the internal essence of quantum world entities. It is impossible for an entity like an electron to have both precise momentum and precise position. It really cannot "know" where it is and where it is going at the same time.
As far as daily standards are concerned, this effect is very small-in the standard unit system with the mass in grams, the value of H is about equal to10-34; This is a measure of the position uncertainty (in centimeters) of an object weighing about 1 gram. The greater the mass of the object, the smaller the uncertainty. For an electron with a mass of only 10-27 grams, its influence is very significant.
The importance of this uncertainty to astronomy lies in the same type of relationship between the energy of an object or even an empty space area and the length of time it is observed. If you observe something carefully for a long time, you can accurately measure its energy at will. But if you just glance at it, energy-not only the energy you measure, but also the real energy-is always uncertain. Just as a quantum entity does not "know" its exact position, it (and the whole universe) does not "know" the exact energy it has in a short time interval. It is this quantum uncertainty that enables electron-positron pairs (and other particle-antiparticle pairs) to emerge from complete nothingness, provided that they annihilate each other in a short time allowed by quantum uncertainty. This is the source of Hawking radiation associated with black holes. It is even possible that the whole universe was created in this way through the skyrocketing in vacuum quantum fluctuations.
The ultimate hope of many physicists is to unify quantum theory and general relativity in a "The Theory of Everything". The test bed of this theory will be to what extent they can explain the nature of the very early universe, because the conditions at that time were far more extreme than those reached by the high-energy collision of particle accelerators on earth.
Copy on page 339 of the Encyclopedia of the Universe.